4. CIRCUIT DESCRIPTION
4-1. POWER SUPPLY circuit
(1) Normal mode
This circuit is an asynchronous switching power supply circuit with using IC901.
Switching frequency is determined on approx. 70kHz oscillation by resistance of R919.
IC905 detects the load of 27V output voltage from the T901 secondary and controls luminescence of PC901
(photocoupler). The 27V output voltage is fed back to pin 9 of IC901. The feedback voltage changes the output pulse
duty of pin 4 of IC901 and stabilize the output voltages from the T901 secondary.
The T901 secondary provides the following DC voltages:
Q
80V line:
Supplied to the HIGH VOLTAGE OUTPUT and the CUT-OFF circuits and the VIDEO OUTPUT
IC as power source.
R
27V line:
Supplied to the HORIZONTAL DEFLECTION OUTPUT (variable B voltage control) circuit as
power source.
S
15V line:
Supplied to the HORIZONTAL DRIVE and the SIGNAL CONTROL circuits and the VERTICAL
OUTPUT IC (+) as power source.
T
–12V line: Supplied to the VERTICAL OUTPUT IC (–) as power source.
- 16 -
AC-IN
T902
IC901
C909
Q901
T901
IC903
IC904
IC906
R919
-12V
5V
CRT HEATER
6.3V
12V
15V
27V
80V
IN
OUT
IN
OUT
IN
OUT
+
+
+
+
+
+
16
15
12
5
3
+
5
4
6
8
D901
1
13
14
7
9
2
10
13
14
17
18
Q901 Drain waveform
IC901 Pin 4 output waveform
Содержание Vision Master 405
Страница 2: ...Revision Record Rev Section Contents...
Страница 35: ...50 49 ASSY 5 ASSY 4 ASSY MONITOR AL 26 25 22 43 44 2 2 21 2 44...
Страница 37: ...15 26 AH 20 16 AA AB 11 A B IC203 J51 ASSY PWB VIDEO 46...
Страница 38: ...7 DIAGRAMS 47...
